Weight reduction to achieve improved fuel economy is perhaps the most critical goals of vehicle manufacturers today. Achieving this goal must be undertaken without sacrificing the structural integrity of the vehicle while at the same time making the vehicle affordable.
The central approach being taken by manufacturers today toward increased vehicle fuel economy has been the reduction of material weight. To this end, ventures are being taken to incorporate aluminum into vehicle structures which were, at one time, steel.
One structural component that has been traditionally been formed from steel is the shock tower. The most common shock tower is a multi-piece, stamped steel assembly. This construction offers a very inexpensive method to meet the vehicle's NVH, durability and safety requirements. However, shock towers formed from stamped steel are very heavy, and thus are not a solution to the goal of overall vehicle weight reduction.
A less common approach to shock tower construction is for the shock tower to be formed from aluminum by Vacuum High Pressure Die Casting (VHPDC). While resulting in a tower that is lighter than steel, the product is more expensive than its steel counterpart. Particularly, the process for manufacturing an aluminum shock tower by way of VHPDC is very intensive, as the production method relies upon a vacuum assist HPDC machine. The resulting product must be subjected to x-ray examination to check porosity. The product must also be heat treated to improve the properties, straightened to remove the warping which occurs during heat treatment, and then subjected to machining of any holes and attachment surfaces.
In addition to a cumbersome and labor-intensive manufacturing process, aluminum shock towers are typically over-designed to compensate for the challenges faced in the VHPDC process. Specifically, the process requires that the minimum wall stock be approximately 2.5 mm in thickness, provided that ribbing is added to provide the minimum structural integrity. However, the minimum thickness results in a heavier and thus more expensive shock tower, undermining the very benefit that aluminum-bases production was intended to achieve.
While known vehicle shock towers function to meet most expectations, they suffer from either being too heavy, as is the case for steel shock towers, or are too expensive to produce, as is the case for aluminum shock towers. Accordingly, a practical alternative to known shock towers is desired.